Mobility impairments are costly in personal, familial, and socioeconomic terms. Surprisingly, there is no consensus on how best to assess mobility, particularly in the elderly people with one or more physical and/or cognitive disabilities who are the focus of this research. The overall goals of this research are to use simple methods to validate and improve the assessment of mobility and its impairments in the elderly. The specific goals include using biomechanically well-controlled balance, gait and transfer tasks of varying difficulty to assess how able and impaired subjects' physical capabilities match or fail to match these task requirements as assessed by Projects 2, 3 and 4. Mobility status will be assessed in tasks involving elements of those of daily living in 600 mostly elderly subjects divided by self-report questionnaire into able, slightly disabled and moderately disabled groups with a range of physical and cognitive impairments; 180 will have Parkinsonism. Each subject will be evaluated in 26 Lo-tech tests of: a) chair rise, b) standing balance, and c) gait and obstacle avoidance tasks with different known functional requirements . Measures of task performance, including numbers of tests satisfactorily completed, will be correlated with a) results of the self assessment questionnaire, (b) measured physical capabilities in terms of strength, joint ranges-of-motion, vision, vestibular function, proprioception, and reaction time, and (c) neuropsychological measures of mental status, cognition and affect. The hypothesis will be tested that performance on one or more tests can be predicted from knowledge of the physical and/or neuropsychological impairments. Data will also be passed to Core B and Projects 2, 3 and 4 for the testing of Program-wide and Project-specific hypotheses. The insights gained from this study will be useful in the design of more effective mobility assessment techniques as well as more effective diagnostic and therapeutic procedures.